The standard assembly sequence for stacked die assemblies when one die is a singulated TSV die with protruding TSV tips on its bottomside and bonding features (e.g., pillars with solder caps) on its topside is generally one of two methods which each involve thermo-compression (TC) bonding. As known in the art, TC bonding involves heating a heated workholder which holds the part being bonded to while applying a compressive force in a bond head contact zone. For example, typical TC bonding conditions can comprise a time of 5 to 10 seconds, a temperature of 150 to 300° C., and a compressive force of ˜1-2 gram force (gf)/bump, which for 500 bumps with 2 gf/bump equals a 1,000 gf total force (=10 N).
A first conventional stacked die assembly method including TSV die involves optionally attaching a package substrate to carrier wafer, flip chip attaching a singulated TSV die having protruding and exposed TSV tips on the bottomside of the TSV die to the package substrate so that the TSV tips face up, and then attaching a singulated second die to the exposed TSV tips. This approach places the exposed TSV tips in the bond head contact zone where bond head force is applied directly to the TSV tips during TC attachment of the TSV die to the package substrate. As a result, the TSV tips, TSVs, and/or the surrounding low-k dielectric layers may be damaged by the applied pressure and/or heat during this TC attachment step.
A second conventional stacked die assembly method including TSV die involves TC bonding for attaching a singulated TSV die having TSV tips on the bottomside of the TSV die face-up to a second die that is in wafer form. In this approach the bonding features (e.g., pillars with solder caps) on the topside of the TSV die are in the bond head contact zone and thus directly receive the bonding head force. As a result, the bonding features (e.g., pillars with solder caps) on the topside and/or the surrounding low-k dielectric layers may be damaged by pressure and/or heat during the TC attachment.
Accordingly, conventional TC attachment of singulated TSV die having TSV tips in a die-to-die or die-to-wafer assembly process has a tendency to damage the bonding terminals features (e.g., pillars with solder caps), the TSV tips, the TSVs themselves and/or adjacent layers (e.g., low-k dielectrics) on the TSV die during the assembly process. Such damage can significantly reduce yield for stacked die devices and also lead to reliability failures in the field. What is needed is new assembly sequences for attaching singulated TSV die having bondable protruding features in a die-to-die or die-to-wafer assembly process which minimizes or eliminates this damage.